In recent years, hydrotherapy vessels have become popular for both medical and social use. While in the past use of hydrotherapy vessels was generally limited to medical or physical therapy, such as for athletes to relieve pain and increase circulation for muscle injuries, more recently the use of hydrotherapy vessels for social purposes and relaxation has undergone spectacular growth. Units may be located outdoors, either in conjunction with a swimming pool or independently, or may be included as a part of a bathtub which is equipped with water circulating mechanisms. The outdoor units are usually relatively large, holding from about 150 to about 800 gallons of water, and require the addition of chemicals to modify water pH and control bacteria growth. Indoor units, such as bathtubs, are usually sufficiently small to justify a separate filling for each use. Prior to use, these tubs are filled with water from the home hot water supply source, and are drained immediately after the use has been completed.
Hydrotherapy bathtubs are generally molded shells which have jet nozzles located at various points on the interior of the tub. A circulating pump brings water from a location near the tub bottom, generally near the drain, and pumps it through the jets thereby creating desired turbulence. Air intake ports built into the jet permit air to be sucked into the jet in large quantities according to the Bernouilli effect, creating a large volume of fluid flow.
Hydrotherapy pumps used in connection with these tubs are generally small centrifugal pumps having a pump impeller which rotates in a vertical plane, and which have an inlet in the pump casing located in a center portion of the casing and an outlet at the top of the casing. The pump casing defines a relatively narrow disc-shaped chamber in which the pump impeller is mounted.
It is conventional for the hydrotherapy pump to be slightly elevated above the tub drain, with the piping connecting the pump inlet to the drain being slightly inclined to permit excess water in the system to drain back through the pump inlet and out the tub drain when the pump is shut off. However, it has now been found that a small amount of water, generally less than one-half cup, remains in the bottom of the pump casing after use of the pump has ceased. This water is unable to drain from the pump casing because the lowest portion of the pump inlet is located at a point above the bottom of the impeller chamber within the pump casing. For most instances of use of commercially available centrifugal pumps, the existence of a small residue of water after use would not create a problem; an exception, however, is the use of centrifugal pumps in freezing weather, when the pump must be completely drained during protracted periods of non-use. For example, a water supply pump for a mountain cabin could be severely damaged if actuated when ice existed in the casing.
In hydrotherapy tubs, the water retained in these pumps may become a breeding ground for harmful bacteria and molds, and may be a source of unpleasant odors. Since several days or weeks may pass between uses of hydrotherapy tubs, particularly in hotels and motels, the existence of a stagnant residue of water at the bottom of the pump casing may create a health hazard, including the possibility of exposure to communicable diseases, in addition to objectionable odors. The present invention provides a method and a fitting for permitting the removal of substantially all of the water in the pump casing after the hydrotherapy pump is shut off.
Accordingly, it is an object of the present invention to provide a pipe fitting which attaches to the conventional inlet of a hydrotherapy pump and also has a conduit which communicates with an opening at a bottom portion of the impeller chamber. It is another object of the invention to provide a fitting which attaches to the pump inlet and also connects with an opening in the casing in an area normally occupied by the freeze plug of the pump. It is yet a further object of the invention to provide a pipe fitting for attachment to the pump inlet which also provides drain means for permitting drainage of substantially all water remaining in the impeller chamber of a centrifugal pump. These and other objects of the invention are accomplished through the use of the method and device of the invention, a specific embodiment of which is set forth in detail herein.